Just because your brother has adhd
doesn't mean he can't be a "kid" & act like one.
Kids "turn off" their moms regularly, like charley brown's teacher - wawawa- & it has nothing to do with adhd. On the other hand, if his adhd is under treated, his symptoms may emerge at night & present as you describe. This should be discussed with his doctor. Ask if you can fill out a questionnaire on him.